Narrow steel edges with a rectangular cross section are generally set into the edges of the running surfaces of skis. These steel edges require resharpening from time to time. Sharpening machines are known for this purpose, but they can only be installed permanently, usually only in sporting goods shops or the like, because of their size and weight. In addition, files are known for sharpening the edges of skis, with which the steel edges can be touched up by hand. However, it is very difficult to produce perfect rectangular edges with such files.